One advantage of the arrangement for generating steering-supporting braking torques MB and/or steering-supporting drive torques MA according to the present invention is the fact that this arrangement may be integrated in the electronic traction control system of vehicle 1 at a relatively low cost. Systems such as ABS, ASR, ESP are already standard in today""s vehicles.
The present invention relates to a vehicle.
European Published Patent Application No. 0 295 396 describes a vehicle that includes at least four wheels, at least one drive axle, one power train which connects a vehicle engine to the drive axle via a transmission, a clutch, and an axle differential, a brake system, which allows each wheel to be braked independently of the other wheels, a steering system, which has a manual steering device such as a steering wheel, at which a driver can set a steering angle for the steerable wheels, and a control system, which brakes at least the drive axle wheel inside the curve below a certain vehicle velocity, for example, 25 km/h, and as of a certain steering angle, for example, 90% of the maximum steering angle, and generates a steering-supporting braking torque on this wheel. In such a vehicle, single-sided braking of the vehicle can thus be performed through which a yaw moment into the curve to be traveled can be generated. The steering action set by the steering angle can thus be supported.
In such a vehicle, steering-supporting braking sequences are implemented using devices that are already present in the vehicle. For example, such a steering-supporting brake system may be constructed using components of an antilock braking system or a traction control system.
German Published Patent Application No. 36 37 481 describes a motor vehicle, in particular a tractor, equipped with a steering brake system in order to implement extremely small turning radii for the vehicle. In this vehicle, a steering brake reversing valve is arranged so that it is functionally linked to a steering system of the motor vehicle, the steering brake reversing valve being activated by the steering system for a certain steering angle of the steered wheels. The wheel of the driven rear axle inside the curve is braked to achieve a steering-supporting braking torque.
Furthermore, German Published Patent Application No. 42 24 887 describes a vehicle, in particular a farm tractor, which includes an electrical and/or electronic controller which issues control signals to pressure medium-controlled brakes of the drive axle wheels, as a function of the steering angle, so that when a predefinable limit steering angle is exceeded, the rear axle wheel inside the curve is braked. Using these measures, the track arc diameter is reduced when traveling around a curve. The steering device preferably sets this steering-supporting braking action so that it continuously increases with an increasing steering angle.
If the left- and right-hand wheels are driven via an axle differential, which can be locked by a differential lock, it is advantageous if the locking action is suspended automatically by the electrical controller if in such a vehicle the controller issues a braking signal to one of the brakes to support steering.
It is an object of the present invention to provide a vehicle in which the steering-supporting action of the brake intervention is improved.
The present invention is based on the concept of taking into account the status of the transmission gear contained in the power train and, additionally or as an alternative, the status of the clutch contained in the power train when setting the intensity of the steering-supporting braking torque. For example, if the clutch is disengaged and/or when the gear is set to neutral, the steering-supporting action may be improved if a different, in particular, stronger braking action is generated on the wheel inside the curve than when the vehicle is in gear and the clutch is engaged.
By taking into account the status of the transmission and/or the clutch, the steering-supporting action of the braking torque generated may thus be improved.
The clutch may be controlled by a control system, the control system causing the clutch to be engaged if the clutch is disengaged in order to generate the steering-supporting braking torque. Taking into account the status when setting the intensity of the braking forces is thus also manifested in the clutch being engaged if required.
In another example embodiment of the present invention, the transmission may be controlled by a control system, the control system causing a gear to be engaged if the transmission was in neutral in order to generate the steering-supporting braking torque, a control system activating the clutch accordingly. In this example embodiment, taking into account the status of the clutch and the transmission is manifested in a gear being automatically engaged by the control system if the transmission was in neutral.
The control system may activate the engine, the transmission, and the clutch in order to generate the steering-supporting braking torque so that a steering-supporting drive torque is additionally generated on the drive axle wheel outside the curve. By this measure, in addition to the braking torque generated on the drive axle wheel inside the curve, an additional drive torque is generated on the drive axle wheel outside the curve, whereby the resulting steering torque may be increased. A dynamic driving situation (e.g., acceleration of the vehicle) intended by the driver may also be taken into account in a suitable manner.
In a vehicle having a power train equipped with a controllable clutch and a controllable transmission, in particular with an automatic transmission having a torque converter, driving situations may arise in which the clutch and/or the transmission are operated so that no engine torque is transmitted to the drive axle. In such a driving situation, the above-mentioned aspect of the present invention is particularly noticeable, since when traveling along a, e.g., sharp, curve, the engine, transmission, and clutch may be controlled so that an engine torque is transmitted to the drive axle, the braking of the wheel inside the curve in conjunction with the axle differential resulting in the additional drive torque being generated on the wheel outside the curve. Even in other operating states of the vehicle in which an engine torque is transmitted to the drive axle through the engaged clutch and through an engaged gear, the present invention may generate an additional drive torque on the wheel outside the curve by adjusting the engine torque accordingly.
The achievable steering torque may be increased by the fact that the control system additionally brakes the wheel inside the curve of at least one non-driven axle, generating a steering-supporting braking torque thereon.
The control system may activate the engine and the clutch in order to support steering so that the variation of the sum of the drive torques generated on the drive axle wheels over time is constant. This arrangement may prevent vehicle responses that are unexpected by the driver.
In a vehicle that is equipped with an activatable additional drive axle, the control system may activate the additional drive axle and a steering-supporting braking torque may also be generated on the wheel inside the curve of the activatable drive axle and a steering-supporting drive torque may be generated on the wheel outside the curve of the activatable drive axle in order to achieve steering support. With this measure, in vehicles with a plurality of drive axles, for example, off-road vehicles or all-wheel drive vehicles, the turning radius, for example, for parking or maneuvering, may be significantly reduced.
A center differential may be provided, which causes the rotational speed to be distributed between the driven front axle and the driven rear axle, this center differential having a differential lock that may be controlled by the control system, the control system operating this differential lock in order to lock the center differential and generate the steering-supporting drive torques. With this measure, constant speed ratios may be guaranteed at the front axle and the rear axle in order to achieve reproducibility of the steering-supporting action of the brake interventions and of drive torque generation.
According to an example embodiment of the present invention, in a vehicle having an electronic traction control system, for example, ABS, ASR, ESP, the control system may be integrated in this traction control system in terms of its hardware and/or implemented in this traction control system in terms of its software. With this measure, in a vehicle having a traction control system, a steering-supporting braking torque, for example, in order to reduce the turning radius or improve maneuverability, may be implemented without requiring additional units to be installed in the vehicle. In the simplest case, it is sufficient to implement a software module in the traction control system. This arrangement makes it possible to retrofit the steering braking system function in a vehicle having a traction control system with minimum expenditure.
It should be understood that the above-named features and those to be explained in detail below may be used not only in the combination described, but also in other combinations or by themselves without departing from the scope of the present invention.